January 2014
Message 35

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[Met-jobs] Post-doctoral Position at L-IPSL (France)

From "Roger Brugge" <>
To "" <>
Date Thu, 16 Jan 2014 09:17:03 +0000

Forwarded from CLIMLIST...

The laboratory of excellence L-IPSL
<> of the
Institut Pierre-Simon Laplace offers a 2-year post-doctoralposition to
work on climate change modeling over West Africa.


The Sahel has undergone a severe (large scale and long-lasting) drought
in the 1970s-1980s. West Africa has also undergone a strong paleo
variability, with evidence for a “green Sahara” about 6000-7000 years
ago. The recent Sahelian drought was probably in large part driven by
the decadal variations of the sea surface temperature. For people of
that region who crucially rely on the monsoon rainfall, anticipating the
possible future variations of the African monsoon system is of great
importance. However, coupled ocean-atmosphere climate model still show a
rather poor skill in simulating the African monsoon, and there is still
a large spread of climate projections on that region. The downscaling
experiments performed under the Cordex program (which did prioritize the
African continent), are at least as dispersed and biased as those from
the global models. Despite the important dispersion, CMIP5 models
suggest a general tendency to a reinforcement of rainfall in central
Sahel, with a slight drying on the Senegal/Guinea coast. This signal may
be related to some robust features found in idealized simulation that
show that CO2 increase produce a rapid reinforcement of ascending
motions in the tropics. This effect could be reinforced by a regional
water vapor positive feedback: increased convergence over the Saharan
heat low brings more water which in turns strengthens regionally the
greenhouse effect. This mechanism share similarities with the response
of monsoon to enhanced Northern hemisphere seasonal insulation that
prevail during the “green Sahara” period. The general purpose of the
work would be twofold: 1) identify the elements of robustness in climate
simulations (paleo, historical reconstructions and climate change
projections), analyzing the contribution of for instance change in large
scale circulation and SSTs, direct CO2 forcing or regional water
feedback, and 2) question the strategies for downscaling experiments
over West Africa as to their ability to account for the identified
critical mechanisms.

Description of work:

The work will be based in part on the multi-model analysis of CMIP5
simulations (in order to identify robust mechanisms and features),
benefiting from the fact that the same model has been used for past
climate, historical simulations and climate change projections. A
particular focus will be put on the analysis of the radiative forcing
(CO2 and aerosols) and feedback (water vapor) over the Saharan heat low.
To test physical hypotheses about the role of these forcings and
feedbacks on climate change over West Africa, the analysis of existing
simulations will be complemented by dedicated simulations with the LMDZ
atmospheric general circulation model, which is the atmospheric
component of the IPSL Coupled Model (involved in CMIP5). The model can
be run either in global mode or zoomed over a particular region of the
globe. It can be run either in climatic mode or “nudged” toward the
large scale dynamics of the reanalysis or the results of another
simulation. The LMDZ physical package has also been coupled to the
dynamics of the WRF regional model, which will allow to test the use of
limited area model without modifying the physics. This suite of
configuration will be used 1) to separate local feedbacks from large
scale couplings (using nudging or not at the boundary of the domain, or
imposing idealized diabatic heating like albedo patches over a region,
or more or less interactions with surface), and 2) to perform
big-brother experiments to compare and assess the strengths and
limitations of different downscaling approaches: a reference simulation
run with a fine global regular grid is used as a reference (or model
truth) for various approaches (zoom with or without nudging, limited
area versions).

Supervision team:The work will be conducted under the main supervision
of Frédéric Hourdin from Laboratoire de Météorologie Dynamique
<> and Sophie Bastin from Laboratoire
Atmosphères, Milieux, Observations Spatiales
<> together with colleagues from the two teams
(Cyrille Flamant, Sandrine Bony, Jean-Louis Dufresne....). The work will
be performed in alternance between the two labs with a schedule to be
discussed, and followed jointly by a larger Labex team who will also
imply P. Braconnot (LSCE <>)...

Experience: The applicant will have experience with numerical modeling
of the Earth system based on global or regional model. He/she also have
experience with handling large datasets. The applicant publication
record should show a majority of papers published in English in top
ranking journals.

Duration and salary: The post-doctorate will be recruited for 24
months with a net monthly salary around 2000 euros, commensurate with
experience. This includes social services and health insurance.

Contact for applications:Applications should include a CV, a statement
of research interestsand the names of at least two references including
e-mail addresses and telephone numbers.

Applications should be submitted by e-mail to Cyrille Flamant
( <>)
before 15 March 2014.

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